Strange the T-nut didn't come away from the wood with the torque you prolly used. That's good! Putting some penetrating oil on the bolt and waiting a few minutes always works. 3 In 1 is good, gun shops sell better.Called "Break Free". Even the most tenuous connection should drive the Delta. Maybe the speaker itself is bad. Voice coil came loose in shipping? The casting that holds the g-nurled knobs is quite fragile. I broke mine and had to JBWeld it back on. That's what you have, right, knurled nut? Not a spade connector? Possibly the wire from there to the motor is loose?